This application is a continuation-in-part of U.S. patent application Ser. No. 09/427,138, filed Oct. 25, 1999 entitled xe2x80x9cEnvironmental Barrier Material for Organic Light Emitting Device and Method of Makingxe2x80x9d which is a continuation-in-part of U.S. patent application Ser. No. 09/212,779, filed Dec. 16, 1998, now U.S. Pat. No. 6,268,695 entitled xe2x80x9cEnvironmental Barrier Material for Organic Light Emitting Device and Method of Making.xe2x80x9d
The present invention relates to organic light emitting devices (OLEDs), and more particularly to OLEDs encapsulated in barrier stacks.
There is a need for versatile visual displays for electronic products of many different types. Light emitting diodes (LEDs) and liquid crystal displays (LCDs) have found many useful applications, but they are not adequate for all situations. OLEDs are a relatively new type of visual display which has shown great promise. An OLED basically includes an organic electroluminescent substance placed between two electrodes. When an electric potential is applied across the electrodes, the electroluminescent substance emits visible light. Typically, one of the electrodes is transparent, allowing the light to shine through. U.S. Pat. Nos. 5,629,389 (Roitman et al.), 5,747,182 (Friend et al.), 5,844,363 (Gu et al.), 5,872,355 (Hueschen), 5,902,688 (Antoniadis et al.), and 5,948,552 (Antoniadis et al.), which are incorporated herein by reference, disclose various OLED structures.
The use of OLEDs in flat panel displays and other information display formats is limited by the poor environmental stability of the devices. G. Gustafson, Y. Cao, G. M. Treacy, F. Klavetter, N. Colaneri, and A. J. Heeger, Nature, Vol. 35, Jun. 11, 1992, pages 477-479. Humidity and oxygen significantly reduce the useful life of most OLEDs. As a result, these devices are typically fabricated on glass substrates with glass covers laminated on top of the OLED and with the edges sealed to exclude water and oxygen from the active layers. U.S. Pat. No. 5,872,355 discloses the use of a polymer such as saran to seal the device. The water vapor permeation rates (WVTR) required to provide sufficient lifetime for OLEDs is calculated to be approximately 10xe2x88x926 g/m2/day. The best polymer films (such as saran) have WVTR values that are 5 orders of magnitude too high to be considered for OLED encapsulation. Furthermore, saran cannot be deposited using flash evaporation, condensation, and in situ polymerization within a vacuum chamber.
Thus, there is a need for an improved lightweight, barrier construction which can be used to encapsulate the OLED and prevent the deterioration caused by permeation of oxygen and water vapor and for a method of making such an encapsulated OLED.
These needs are met by the present invention which is an encapsulated organic light emitting device (OLED). In one embodiment, the encapsulated OLED includes a substrate, an organic light emitting device adjacent to the substrate, and at least one first barrier stack adjacent to the organic light emitting device, the at least one first barrier stack comprising at least one first barrier layer and at least one first decoupling layer, wherein the at least one first barrier stack encapsulates the organic light emitting device. By xe2x80x98adjacent,xe2x80x99 we mean next to, but not necessarily directly next to. There can be additional layers intervening between the adjacent layers.
Optionally, there can be at least one second barrier stack adjacent to the organic light emitting layer device and located between the substrate and the organic light emitting device. The second barrier stack has at least one second barrier layer and at least one second decoupling layer. The first barrier stack can be substantially transparent, the second barrier stack can be substantially transparent, or both the first and second barrier stacks can be substantially transparent, depending upon the particular application. At least one of the first or second barrier layers may be made from a material including, but not limited to, metals, metal oxides, metal nitrides, metal carbides, metal oxynitrides, metal oxyborides, and combinations thereof. Metals include, but are not limited to, aluminum, titanium, indium, tin, tantalum, zirconium, niobium, hafnium, yttrium, nickel, tungsten, chromium, zinc, alloys thereof, and combinations thereof. Metal oxides include, but are not limited to, silicon oxide, aluminum oxide, titanium oxide, indium oxide, tin oxide, indium tin oxide, tantalum oxide, zirconium oxide, niobium oxide, hafnium oxide, yttrium oxide, nickel oxide, tungsten oxide, chromium oxide, zinc oxide, and combinations thereof. Metal nitrides include, but are not limited to, aluminum nitride, silicon nitride, boron nitride, germanium nitride, chromium nitride, nickel nitride, and combinations thereof. Metal carbides include, but are not limited to, boron carbide, tungsten carbide, silicon carbide, and combinations thereof. Metal oxynitrides include, but are not limited to, aluminum oxynitride, silicon oxynitride, boron oxynitride, and combinations thereof. Metal oxyborides include, but are not limited to, zirconium oxyboride, titanium oxyboride, and combinations thereof.
Substantially opaque barrier layers can be made from opaque materials including, but not limited to, opaque metals, opaque polymers, opaque ceramics, opaque cermets, and combinations thereof. Opaque cermets include, but are not limited to, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, niobium nitride, tungsten disilicide, titanium diboride, zirconium diboride, and combinations thereof.
The barrier layers in the first and second barrier stacks can be made of the same material or a different material. Barrier layers within the first or second barrier stacks can be the same or different.
The substrate can be either a flexible substrate or a rigid substrate. Flexible substrates include, but are not limited to, polymers, metals, paper, fabric, glass, and combinations thereof. Rigid substrates include, but are not limited to, ceramics, metals, glass, semiconductors, and combinations thereof.
The decoupling layers of the first and second barrier stacks can be made from materials including, but not limited to, organic polymers, inorganic polymers, organometallic polymers, hybrid organic/inorganic polymer systems, and silicates. Organic polymers include, but are not limited to, (meth)acrylates, urethanes, polyamides, polyimides, polybutylenes, isobutylene isoprene, polyolefins, epoxies, parylene, benzocyclobutadiene, polynorbomenes, polyarylethers, polycarbonate, alkyds, polyaniline, ethylene vinyl acetate, and ethylene acrylic acid. Inorganic polymers include, but are not limited to, silicones, polyphosphazenes, polysilazne, polycarbosilane, polycarborane, carborane siloxanes, polysilanes, phosphonitriles, sulfur nitride polymers and siloxanes. Organometallic polymers include, but are not limited to, organometallic polymers of main group metals, transition metals and lanthanide/actinide metals (for example, polymetallocenylenes such as polyferrocene and polyruthenocene). Hybrid organic/inorganic polymer systems include, but are not limited to, organically modified silicates, ceramers, preceramic polymers, polyimide-silica hybrids, (meth)acrylate-silica hybrids, polydimethylsiloxane-silica hybrids. The decoupling layers in the first and the second barrier stacks can be the same or different. Decoupling layers within the first and second barrier layers can be the same or different at 23xc2x0 C. and 0% relative.
The encapsulated organic light emitting device can have an oxygen transmission rate through the at least one first barrier stack of less than 0.005 cc/m2/day at 23xc2x0 C. and 0% relative humidity, an oxygen transmission rate through the at least one first barrier stack of less than 0.005 cc/m2/day at 38xc2x0 C. and 90% relative humidity, or a water vapor transmission rate through the at least one first barrier stack of less than 0.005 gm/m2/day at 38xc2x0 C. and 100% relative humidity.
There can optionally be a functional layer adjacent to the substrate and located between the substrate and the organic light emitting device. There can also be a functional layer adjacent to the first barrier stack on a side opposite the organic light emitting device, if desired.
The encapsulated organic light emitting device can optionally include a protective layer adjacent to the at least one first barrier stack on the side opposite the organic light emitting device.
Another embodiment of the invention involves an encapsulated organic light emitting device including at least one second barrier stack comprising at least one second barrier layer and at least one second decoupling layer, an organic light emitting device adjacent to the at least one second barrier stack, and at least one first barrier stack adjacent to the organic light emitting device, the at least one first barrier stack comprising at least one first barrier layer and at least one first decoupling layer, wherein the at least one first barrier stack and the at least one second barrier stack encapsulate the organic light emitting device. The encapsulated OLED optionally includes a substrate adjacent to the at least one second barrier stack on the side opposite the organic light emitting device.
The invention also involves a method of making encapsulated organic light emitting devices. The method includes providing a substrate having an organic light emitting device thereon, and placing at least one first barrier stack adjacent to the organic light emitting device to encapsulate the organic light emitting device, the at least one first barrier stack comprising at least one first barrier layer and at least one first decoupling layer.
Placing the at least one first barrier stack adjacent to the organic light emitting device includes, but is not limited to, depositing the at least one first barrier stack adjacent to the organic light emitting device, and laminating the at least one first barrier stack adjacent to the organic light emitting device. Depositing the at least one first barrier stack includes, but is not limited to, depositing the at least one first barrier stack in vacuum, depositing the at least one first barrier stack at atmospheric pressure, and depositing the at least one first barrier layer in vacuum and depositing the at least one first decoupling layer at atmospheric pressure. Methods of laminating the at least one first barrier stack adjacent to the organic light emitting device include, but are not limited to, laminating by heating, soldering, ultrasonic welding, applying pressure, and using an adhesive.
Providing the substrate having the organic light emitting device thereon includes, but is not limited to, providing the substrate, and placing the organic light emitting device adjacent to the substrate. Placing the organic light emitting device adjacent to the substrate includes, but is not limited to, depositing the organic light emitting device adjacent to the substrate, and laminating the organic light emitting device adjacent to the substrate. Depositing the organic light emitting device includes, but is not limited to, depositing the organic light emitting device in vacuum.
At least one second barrier stack may be placed adjacent to the substrate before the organic light emitting device is placed thereon so that the organic light emitting device is encapsulated between the at least one first and second barrier stacks, the at least one second barrier stack comprising at least one second barrier layer and at least one second decoupling layer. Placing the at least one second barrier stack adjacent to the substrate includes, but is not limited to, depositing the at least one second barrier stack adjacent to the substrate, and laminating the at least one second barrier stack adjacent to the substrate. Depositing the at least one second barrier stack includes, but is not limited to, depositing the at least one second barrier stack in vacuum, depositing the at least one second barrier stack at atmospheric pressure, and depositing the at least one second barrier layer in vacuum and depositing the at least one second decoupling layer at atmospheric pressure. Methods for laminating the at least one second barrier stack include, but are not limited to, heating, soldering, ultrasonic welding, applying pressure, or using an adhesive.
The substrate can be removed from the encapsulated organic light emitting device if desired, depending on the specific design of the encapsulated OLED and the application.
At least one of the at least one first or second barrier layers can include at least two barrier layers. The at least two barrier layers can be deposited using the same deposition source, or different deposition sources. They can be made of the same barrier material, or different barrier materials. They can be vacuum deposited.
Accordingly, it is an object of the present invention to provide an encapsulated OLED, and to provide a method of making such a device.